I decided to try and really get to the bottom of something today that has been bugging me for ages on my main PC. This "simple problem" has taken me hours to resolve, but I wanted to record on here the actual cause just in case it can help someone else in the same situation.

Ive spent a lot of time scanning various forums, and the Microsoft help site.. and I'll also list some of the common fixes (which wasnt the solution in my case) which is basically the cumilation of hours of work all in one place.

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Windows Media Player/Winamp wont Play .MPG or MPEG files.

Scenario.

.mpg and .mpeg files stored on the computer which previously played ok, no longer work in either WMP or Winamp etc.

If like me, you have a CMedia AC97 (or more specifically a C-Media 9780 7.1 channel), Windows Update sometimes tries to automatically update with the wrong drivers. - I couldnt find the correct drivers on the CMedia site. In the end I uninstalled the windows updated drivers and reinstalled from ended up on the Medion Site where I downloaded and installed Soundcard Driver skcmiac97win9xp.exe which comes which comes with the C-Media Media Center Software. You can also use CMI 9780 5.12.01.0043 whql driver from Softpeadia.

M$ also have some resolutions on their site - One of the errors I got after reinstalling the soundcard drivers, took me to a M$ page which said that WMP needed other software and be associated with to be able to play the video file... Then kindly gave me suggestions of software to buy.. erm no thanks since I knew it previously worked.

Whilst on this track I suddenly realised that the files would actually play in Power DVD which I already had on my PC. Why the files would play in Power DVD yet not in WMP as previously was now a bit of a puzzle - so I spent ages messing around trying to re-associate with WMP or Winamp to no avail. The weird thing here is this is normally a MPEG2 symptom I was seeing but for mpg and .mpeg files.

Check to see if they can work in certain other players.

A bit of research showed that other users were also finding that previously fine mpg and mpegs could also now only be viewed in other software.Players to try that sometimes work are:

It would appear that after updating to WMP11 it can have a habit of not playing some files due to them being tagged as having digial rights. This one is particulary nasty and I'll leave you with more info:-

It may be advisable before doing this to go to C:\Documents and Settings\All Users - In there theres a hidden folder "DRM" and rename it to DRM_old

* Final solution that worked.

I was still unhappy since I much prefer to view files in winamp or WMP and now I'd got this far it was now really bugging me why Id now managed to get them to play in PowerDVD and Quicktime. PowerDVD seemed overkill to me, and I dont like the nag screen or the way quicktime works so Im now thinking there must be a conflict somewhere.

Once I had actually sussed the problem, further googling under my phone model, revealed that the Samsung Phone PC Studio software that came with my D900 actually seems to stop mpg and .mpeg problems from playing. This is the thread I found after spending hours trying to solve the problem myself, and after Id already typed out most of this post already. :(